TUBICOLAR ANNELIDA. 
13 
sents ail the phases of development from the convolute, spirorbiform condition 
to the nearly straight forms, and all have a very similar aspect to the speci¬ 
men represented in figures 1 and 2 of the same plate. We know it only in its 
immature condition, in the single specimen illustrated. 
In figure 41 the tubes are somewhat more slender and more fiexuous than in 
specimens of the same degree of development from the region around Cincin¬ 
nati, and this form will probably prove a distinct species. Tlie figure is from 
the original specimen, described as Tentaculites ? flexuosus, from the Trenton lime¬ 
stone (Pal. N. Y., vol i, p. 92, pi. xxix, figs. 6a-d). Want of material will 
prevent a complete comparison and final discussion of the relations of this 
species with any other, at the present time. 
The forms illustrated on plate Ixxii, figs. 2 a and b. Pal. N. Y., vol. i, p. 284, 
were referred to the species Tentaculites Jlexuosa, the ? after the generic 
name being accidentally omitted. A comparison was also suggested with Cor- 
nulites serpularius, Schlotheim (Murchison’s Sil. Syst., p. 627, pi. xxvi, figs. 5-8). 
The specimens from the Hudson River group of New York are, however, 
more slender and are frequently regularly curved, not fiexuous as in the typical 
form of T. ? flexuosus, from the Trenton limestone. They are very similar to, 
and perhaps identical with those from the same horizon in the west, and their 
probable identity with the western forms was at that time recognized in citing 
the localities. 
We come now to consider some forms of this genus known to us in the 
higher rocks, and more especially the single species occurring in the Niagara 
group at Waldron, Indiana. The material at hand is not so complete in some 
respects as that from the Hudson River group of the Cincinnati region, repre¬ 
sented on plate cxv. In its entire aspect, however, it presents the same phases 
of development, and we have more complete material to illustrate the advanced 
stages of growth in this species. The earliest condition in which their specific 
relations usually are observed, is that of groups of slender, fiexuous, or rarely 
almost straight tubes, attached on one side for nearly or quite their entire length 
to some other organisms, as the shell of a Brachiopod, a Gastropod, or the calyx 
of a Grinoid. In this condition the apertures are frequently turned outward. 
